Rotor and motor having same

Abstract

A rotor and a motor having same are disclosed. The rotor comprises a U-type permanent magnet. The U-type permanent magnet can use a greater amount of magnet material than a C-type permanent magnet. The permanent magnet includes an arc portion and a plurality of straight portions. The straight portions can extend in the radial direction from one end of the arc portion. The angle between the inner surfaces of the straight portions can be greater than the angle between the outer surfaces of the straight portions. Therefore, torque ripples can be reduced.

Description

Rotor and motor equipped with the same

[0001] The present invention relates to a rotor capable of improving torque as well as torque ripple, and a motor equipped with the same.

[0002] Permanent magnet motors can be classified into permanent magnet surface-mounted motors and permanent magnet embedded motors depending on the coupling structure of the permanent magnets.

[0003] In surface-mounted permanent magnet motors, the permanent magnet is attached to the surface of the core. In embedded permanent magnet motors, the permanent magnet is installed embedded inside the core.

[0004] Prior art document JP 2012-050189 A (published March 8, 2012, hereinafter referred to as "Patent Document 1") discloses an electric motor, a hermetic compressor having the same, and a refrigerator having the same.

[0005] According to Patent Document 1, in order to achieve high efficiency with a low-cost permanent magnet having low magnetic flux density, such as a ferrite magnet, a permanent magnet in the shape of an arc segment having three-axis anisotropy is mounted on the rotor, so that magnetic field lines from the permanent magnet are generated in the directions M1, M2, and M3, thereby increasing the amount of effective magnetic flux.

[0006] However, in conventional examples of 3-axis anisotropic shaped magnets, when high efficiency is sought, the difference in magnetic flux density within the gap increases. As a result, torque ripple increases and becomes a cause of noise generated in the motor.

[0007] The above patent document 1 additionally forms a groove on the outer surface of the rotor core to reduce the torque ripple.

[0008] However, there is a problem in that the addition of the above-mentioned groove causes a counterproductive effect of reducing torque.

[0009] Prior art patent document WO 2023 / 054173 A1 (published April 6, 2023, referred to as “Patent Document 2”) discloses a rotor, a motor, a compressor, and a refrigerator.

[0010] According to Patent Document 2, three magnets are used for a single-pole magnet. Two of the three are rectangular magnets, and the remaining one is an arc-shaped magnet. The rectangular and arc-shaped magnets can form a U-shaped magnet.

[0011] Rectangular magnets are magnetized perpendicular to the width of the magnet. Arc-shaped magnets are magnetized parallel to the arc. The center point of the overall magnetization direction of a U-shaped magnet is located within the rotor.

[0012] However, in the case of Patent Document 2, if the magnetization center moves into the interior of the rotor, a problem arises in which cogging torque and torque ripple increase.

[0013] More specifically, when the center of magnetization moves into the rotor, the magnetic flux distribution—that is, the attractive force between the magnet and the stator slot—becomes non-uniform.

[0014] Cogging torque is a variation in torque that occurs in permanent magnet motors due to the interaction between the slots of the stator and the magnets of the rotor. Cogging torque hinders the smooth rotation of the motor and causes irregular movement at low speeds.

[0015] Torque ripple refers to the instantaneous fluctuation in torque that occurs as a motor rotates.

[0016] For example, along the air gap between the stator and the rotor, the magnetic attraction increases at a specific angle in the circumferential direction and decreases at another angle. As the rotor rotates, the attraction changes along the stator slots, causing the cogging torque to increase.

[0017] When the center of magnetization shifts inward into the rotor, the air gap flux density becomes asymmetric, leading to increased fluctuations in electromagnetic force. Additionally, the phase-dependent electromagnetic torque is non-uniform, with more torque generated at certain angles and less torque at others.

[0018] As a result, torque ripple increases, which can have an adverse effect, particularly on servo motors, robots, and electric vehicles that require precise speed and position control.

[0019] The objective of the present invention is to provide a rotor with a structure capable of solving the aforementioned problems and a motor equipped with the same.

[0020] The first objective is to provide a rotor with a structure capable of increasing the use of permanent magnets in a limited space, and a motor equipped with the same.

[0021] The second objective is to provide a rotor with a structure capable of reducing torque ripple without adding grooves to the rotor core, and a motor equipped with the same.

[0022] The third objective is to provide a rotor with a structure capable of improving torque and efficiency, and a motor equipped with the same.

[0023] The fourth objective is to provide a rotor with a structure that can reduce the stacking length of the rotor core and a motor equipped with the same.

[0024] The fifth objective is to provide a rotor with a structure capable of reducing material costs and a motor equipped with the same.

[0025] As a result of intensive research, the inventors have found that the problem of the present invention or the first to fourth objectives described above can be achieved by the following embodiments of the present invention.

[0026] To achieve the above-mentioned objective, the rotor of the present invention can maximize the amount of magnet used by employing a U-shaped permanent magnet with a high degree of shape freedom consisting of a combination of straight lines and arcs, compared to a C-shaped permanent magnet consisting only of arcs.

[0027] A rotor according to the present invention comprises a plurality of permanent magnets; and a rotor core having a plurality of magnet receiving portions that accommodate the plurality of permanent magnets. The plurality of permanent magnets may include an arc portion; and a pair of straight portions extending radially from each end of the arc portion.

[0028] Each of the above plurality of permanent magnets can be formed as a single unit.

[0029] Through this, torque ripple can be reduced, and noise and vibration can be minimized.

[0030] According to one example, the pair of straight sections may each be formed in a cuboidal shape. The pair of straight sections may include a pair of inner surfaces arranged to face each other in the circumferential direction of the rotor core; and a pair of outer surfaces arranged to be away from the pair of inner surfaces in the circumferential direction.

[0031] The angle between the aforementioned pair of inner surfaces can be formed to be larger than the angle between the aforementioned pair of outer surfaces.

[0032] Through this, torque ripple can be reduced.

[0033] According to one example, the plurality of permanent magnets may be provided as one per pole.

[0034] When the above rotor is configured as a N pole, the angle between the outer surfaces of the pair of straight sections may be (360 / N) ±10°. The angle between the inner surfaces of the pair of straight sections may be greater than the angle between the outer surfaces.

[0035] Through this, the amount of magnets used in a limited space can be increased, reducing the stacking length of the motor while improving torque and efficiency to an equivalent or higher level and reducing torque ripple.

[0036] According to one example, the angle between the outer surfaces of the above pair of straight sections may be (360 / N)°.

[0037] According to one example, the plurality of permanent magnets may be spaced apart in the circumferential direction of the rotor core.

[0038] One straight section of one of the two permanent magnets adjacent in the circumferential direction and one straight section of the other of the two permanent magnets can be arranged adjacent to and parallel to each other.

[0039] According to one example, the inner surface of one of the pair of straight sections may be formed at an angle with respect to the outer surface of the one straight section.

[0040] According to one example, the pair of straight sections may each be formed in a cuboidal shape and include a pair of inner surfaces arranged to face each other in the circumferential direction of the rotor core; and a pair of outer surfaces arranged to be away from the pair of inner surfaces in the circumferential direction.

[0041] The thickness of the straight section is formed between the inner and outer surfaces of the pair of straight sections. The thickness of the straight section may decrease as it extends outward in the radial direction from the arc section. Through this, torque ripple can be reduced.

[0042] According to one example, the radial length of the outer surface of the straight section may be formed to be longer than the radial length of the inner surface of the straight section.

[0043] According to one example, the arc portion may include an inner surface formed in an arc shape and positioned toward the outer surface of the rotor core; and an outer surface formed in an arc shape and positioned toward the center of the rotor core.

[0044] The arc centers of the inner and outer surfaces of the arc portion are the same, and the outer surface of the arc portion can be positioned toward the center of the rotor core.

[0045] Through this, the radial thickness of the arc portion can be formed uniformly along the circumferential direction of the arc portion. The shape freedom of the permanent magnet can be increased.

[0046] According to one example, the thickness of the arc portion may be formed between the outer surface and the inner surface of the arc portion. The thickness of the arc portion may be constant along the circumferential direction.

[0047] According to one example, the permanent magnet may be symmetrical with respect to a virtual centerline passing through the center of the rotor core and the center of the arc of the arc portion.

[0048] According to one example, the angle between the inner surfaces of the pair of straight sections may be greater than 100% and less than or equal to 133.3% compared to the angle between the outer surfaces of the pair of straight sections. Through this, cogging torque and torque ripple can be reduced.

[0049] According to one example, the radial length extending along the center of one of the pair of straight sections may be formed to be smaller than the arc length extending along the center of the arc section.

[0050] Through this, the amount of magnet usage of the above-mentioned permanent magnet can be increased.

[0051] According to one example, the length of the straight section may be within 36% of the arc length of the arc section.

[0052] Through this, the amount of magnets used can be increased.

[0053] According to one example, the magnetization center of each of the plurality of permanent magnets may be located on the outer side of the rotor core.

[0054] Through this, torque ripple can be reduced.

[0055] According to one example, the distance from the center of the rotor core to the center of magnetization of the permanent magnet may be greater than the distance from the center of the rotor core to the center of the arc of the arc portion.

[0056] Through this, torque ripple can be reduced.

[0057] According to one example, the shortest distance between the outer surface of the rotor core and the center of the arc of the arc portion may be greater than or equal to the shortest distance between the outer surface of the rotor core and the outer end of the straight portion.

[0058] According to one example, the arc portion may include an inner surface formed in an arc shape and positioned toward the outer circumference of the rotor core; and an outer surface formed in an arc shape and positioned toward the center of the rotor core. The arc centers of the inner surface and the outer surface of the arc portion may be the same.

[0059] The thickness of the arc portion may be formed between the outer surface and the inner surface of the arc portion. On an imaginary centerline passing through the center of the rotor core and the arc center of the arc portion, the thickness of the arc portion may be greater than or equal to the distance between the inner surface of the rotor core and the outer surface of the arc portion, and less than or equal to the distance between the outer surface of the rotor core and the inner surface of the arc portion.

[0060] Through this, it is possible to maintain an equivalent or higher level of torque while reducing the stack length of the motor.

[0061] A motor according to the present invention comprises: a housing; a stator coupled to the inside of the housing; and a rotor spaced apart from the inside of the stator with an air gap and rotating about a rotation axis with respect to the stator. The rotor may include a plurality of permanent magnets; and a rotor core having a plurality of magnet receiving portions that accommodate the plurality of permanent magnets.

[0062] Each of the above plurality of permanent magnets may include an arc portion; and a pair of straight portions extending radially from each end of the arc portion.

[0063] Each of the above plurality of permanent magnets can be formed as a single unit.

[0064] According to one example of the above motor, each of the plurality of permanent magnets may have a magnetization center located on the outer side of the rotor core.

[0065] Through this, the performance of the motor can be improved.

[0066] According to one example of the above motor, the stator comprises: a stator core having a plurality of teeth and slots alternately arranged along the circumferential direction; and a stator coil wound on the stator core through the slots. A pole shoe may be formed to protrude circumferentially from the radially inner end of the teeth.

[0067] The distance from the center of the rotor core to the magnetization center of the permanent magnet may be greater than the radius of the rotor core and less than 1.05 times the distance from the center of the rotor core to the intersection point of the teeth and the pole shoe.

[0068] Through this, the magnetization center of the permanent magnet is adjusted differently from the arc center of the arc section, thereby improving performance such as the motor's torque and efficiency.

[0069] According to one example of the above motor, the pair of straight sections may each be formed in a cuboidal shape. The pair of straight sections may include a pair of inner surfaces arranged to face each other in the circumferential direction of the rotor core; and a pair of outer surfaces arranged to be away from the pair of inner surfaces in the circumferential direction.

[0070] The angle between the aforementioned pair of inner surfaces can be formed to be larger than the angle between the aforementioned pair of outer surfaces. Through this, torque ripple can be reduced.

[0071] According to one example of the above motor, the plurality of permanent magnets may be provided as one per pole.

[0072] When the above rotor is configured as a N pole, the angle between the outer surfaces of the pair of straight sections is (360 / N) ±10°, and the angle between the inner surfaces of the pair of straight sections may be greater than the angle between the outer surfaces of the pair. Through this, torque ripple can be reduced while satisfying the target torque of the motor.

[0073] According to one example of the above motor, the angle between the outer surfaces of the pair of straight sections may be (360 / N)°.

[0074] According to one example of the above motor, the plurality of permanent magnets may be spaced apart in the circumferential direction of the rotor core.

[0075] One straight section of one of the two permanent magnets adjacent in the circumferential direction and one straight section of the other of the two permanent magnets can be arranged adjacent to and parallel to each other.

[0076] According to an embodiment of the present invention, the following effects can be achieved.

[0077] First, the rotor can be installed such that a permanent magnet is embedded inside the rotor core. The permanent magnet can be formed in a U-shape. The U-shaped permanent magnet can be composed of an arc section and a plurality of straight sections.

[0078] The arc portion may be formed convexly toward the center of the rotor core. Multiple straight portions may extend radially from each end of the arc portion.

[0079] Through this, U-type permanent magnets can increase magnet usage compared to C-type permanent magnets formed only in an arc shape.

[0080] Second, the angle between the inner surfaces of the straight section of the permanent magnet can be formed to be larger than the angle between the outer surfaces of the straight section of the permanent magnet. For example, the angle between the outer surfaces of the straight section of the permanent magnet can be 60 degrees based on a 6-pole configuration. The angle between the inner surfaces of the straight section of the permanent magnet can be formed in the range of 60 to 80 degrees.

[0081] Through this, the permanent magnet can reduce torque ripple while satisfying the target torque.

[0082] Third, the magnetization center of the U-type permanent magnet can be adjusted differently from the arc center of the arc section. For example, the distance from the center of the rotor core to the magnetization center of the permanent magnet can be set to be larger than the radius of the rotor.

[0083] The distance from the center of the rotor core to the magnetization center of the permanent magnet may be 1.05 times or less the distance from the center of the rotor core to the intersection point of the pole shoe and teeth of the stator.

[0084] Through this, the motor's torque and efficiency can be improved.

[0085] FIG. 1 is a conceptual diagram for explaining the configuration of a motor according to an embodiment of the present invention.

[0086] Figure 2 is a top view of the motor in Figure 1.

[0087] Figure 3 is a perspective view showing the rotor in Figure 1.

[0088] Figure 4 is an exploded view showing the permanent magnet in the rotor core disassembled in Figure 3.

[0089] Figure 5 is a top view of the rotor in Figure 3.

[0090] Figure 6 is a cross-sectional view taken along VI-VI in Figure 5.

[0091] Figure 7 is a conceptual diagram for explaining the comparison of magnet usage amounts according to the shape of the magnet.

[0092] Figure 8 is a graph for comparing (a) back electromotive force and (b) torque according to the shape of the magnet.

[0093] Figure 9 is a conceptual diagram for explaining the angle between the outer and inner surfaces of the straight section of the U-shaped magnet in Figure 5 and the length of the straight section relative to the arc length of the arc section.

[0094] Figure 10 is a table showing the straight section-arc section length ratio, torque, and torque ripple according to the angle between the inner surfaces of the straight section in Figure 9.

[0095] Figure 11 is a graph showing the change in (a) torque / torque ripple and (b) torque waveform according to the angle between the inner surfaces of the straight section in Figure 9.

[0096] FIG. 12 is a conceptual diagram for explaining the comparison between the distance between the rotor center and the magnetization center of the permanent magnet, the distance between the rotor center and the arc center, and the distance between the rotor center and the intersection point of the stator pole shoe and teeth in FIG. 2.

[0097] Figure 13 is a table showing the change in torque and torque ripple according to the distance between the rotor center and the magnetization center of the permanent magnet in Figure 12.

[0098] Figure 14 is a graph showing (a) torque / torque ripple and (b) torque waveform according to the distance between the rotor center and the magnetization center of the permanent magnet in Figure 12.

[0099] Hereinafter, a rotor according to an embodiment of the present invention and a motor equipped with the same will be described in detail with reference to the attached drawings.

[0100] In the following description, descriptions of some components may be omitted to clarify the features of the present invention.

[0101] 1. Definition of Terms

[0102] Terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0103] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0104] As used in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0105] In the following description, “radial” or “radial” refers to a shape extending outward from a central point like spokes of a wheel.

[0106] In the following description, “axial direction” refers to the longitudinal direction of the crankshaft.

[0107] In the following description, the term “axial direction” may refer to the vertical direction.

[0108] In the following description, the term “radial direction” refers to the longitudinal direction of a line segment extending from the center of a circle or cylinder to a point on the circumference.

[0109] In the following description, "radial direction" refers to the direction extending outward from the center of an object or point, such as a circle or a sphere.

[0110] In the following description, “circumferential direction” refers to the direction of the circumference.

[0111] In the following description, the crankshaft refers to a shaft that converts rotational motion into linear motion, primarily used to move pistons.

[0112] In the following description, the term "journal" refers to a shaft part supported by bearings, etc.

[0113] In the following description, MPF (Magnet Pull Force) refers to the attractive force between a magnet and a metal or other magnetic material.

[0114] 2. Description of the configuration of a motor according to an embodiment of the present invention

[0115] FIG. 1 is a conceptual diagram for explaining the configuration of a motor according to an embodiment of the present invention.

[0116] Figure 2 is a top view of the motor in Figure 1.

[0117] FIG. 3 is a perspective view showing the rotor (120) in FIG. 1.

[0118] FIG. 4 is an exploded view showing the permanent magnet (126) disassembled from the rotor core (121) in FIG. 3.

[0119] FIG. 5 is a top view of the rotor (120) in FIG. 3.

[0120] Figure 6 is a cross-sectional view taken along VI-VI in Figure 5.

[0121] In this embodiment, the motor may be applied to a compressor. In particular, the motor may be applied to a refrigerator compressor. However, it is not limited thereto.

[0122] The motor includes a housing (not shown), a stator (100), and a rotor (120).

[0123] The housing can form the exterior of the motor. A cover may be provided at both ends or one end of the housing. The cover is configured to cover both ends or one end of the housing. The internal space of the housing may be configured to be sealed.

[0124] A receiving portion is formed inside the housing to accommodate the stator (100) and the rotor (120).

[0125] The stator (100) may include a stator core (110) and a stator coil (115). The stator core (110) may be formed in a cylindrical shape. A rotor receiving hole is provided on the inner side of the stator core (110). The rotor receiving hole may be formed to penetrate along the axial direction from the center of the stator core (110).

[0126] The rotor receiving hole can accommodate the rotor (120) described later. The diameter of the rotor receiving hole can be formed to be slightly larger than the diameter of the rotor (120), for example, twice as large as the air gap.

[0127] The stator core (110) may be configured to have a back yoke (111), a plurality of slots (112), and a plurality of teeth (113). The back yoke (111) may be formed in a cylindrical shape. The back yoke (111) may form the outer surface of the stator core (110).

[0128] A plurality of teeth (113) may be formed to protrude radially from the inner circumference of the back yoke (111) toward the center of the stator (100). A plurality of teeth (113) may be arranged circumferentially spaced apart along the circumference of the rotor receiving hole. A pole shoe (114) may be formed to protrude circumferentially from the inner end of the teeth (113).

[0129] A slot (112) may be formed between a plurality of adjacent teeth (113) in the circumferential direction. A plurality of slots (112) and a plurality of teeth (113) may be arranged alternately in the circumferential direction. A slot (112) may be formed to penetrate along the axial direction of a stator core (110). A slot (112) may provide a passage through which a stator coil (115) penetrates from one axial end of the stator core (110) toward the other axial end.

[0130] Through this, the stator coil (115) can be wound onto the teeth (113) of the stator core (110) through a plurality of slots (112).

[0131] The stator coil (115) may be composed of a plurality of phase coils. The plurality of phase coils may be provided with three strands to be connected to a three-phase AC power source. When the stator coil (115) receives external power, it can form a magnetic field around itself.

[0132] The rotor (120) includes a rotation axis (123) and a rotor core (121). The rotor core (121) may be formed in a cylindrical shape. The rotor core (121) may be constructed by stacking and joining a plurality of electrical steel plates in the axial direction of the rotation axis (123).

[0133] A bearing hole (122) may be provided in the center of the rotor core (121). The bearing hole (122) may be formed to penetrate through the rotor core (121) in the axial direction. The bearing hole (122) may accommodate a rotation axis (123). The diameter of the bearing hole (122) may vary depending on the axial height of the rotor core (121).

[0134] The rotation axis (123) can be coupled to the center of the rotor core (121) through the bearing hole (122). Through this, the rotation axis (123) can rotate together with the rotor core (121). The rotor core (121) can rotate around the rotation axis (123).

[0135] The bearing hole (122) may include a first bearing hole (122a) and a second bearing hole (122b).

[0136] The first bearing hole (122a) may be positioned in the inner lower part of the rotor core (121). The first bearing hole (122a) may have a first diameter. The second bearing hole (122b) may be positioned in the inner upper part of the rotor core (121). The second bearing hole (122b) may have a second diameter larger than the first diameter of the first bearing hole (122a).

[0137] The rotation shaft (123) can be inserted into and coupled to the first shaft receiving hole (122a).

[0138] When a motor is applied to a compressor, the compressor (not shown) may include a housing (not shown) and a frame (not shown). The frame may be provided inside the housing. The frame may include a shaft support (124). The shaft support (124) may have a shaft receiving portion to accommodate a rotating shaft (123). The shaft support (124) may rotatably support a portion of the rotating shaft (123).

[0139] A magnet receiving portion (125) may be provided on the inner side of the rotor core (121). The magnet receiving portion (125) may be formed to penetrate in the axial direction of the rotor core (121). The magnet receiving portion (125) may accommodate a permanent magnet (126). The magnet receiving portion (125) may be formed to correspond to the shape of the permanent magnet (126). The permanent magnet (126) may be coupled to the rotor core (121) through the magnet receiving portion (125).

[0140] The magnet receiving portion (125) may be provided in multiple numbers. The multiple magnet receiving portions (125) may be spaced apart in the circumferential direction along the circumference of the shaft receiving hole (122).

[0141] The rotor (120) may include a permanent magnet (126) to generate a magnetic field.

[0142] The permanent magnet (126) may be composed of a U-type permanent magnet (126). Here, the term U-type is named as such because the shape of the permanent magnet (126) is similar to the shape of a U.

[0143] The U-type is a shape that combines straight lines and arcs. The permanent magnet (126) can be formed as a single unit.

[0144] The permanent magnet (126) according to the present embodiment may be configured to include an arc portion (127) and a straight portion (130).

[0145] Permanent magnets (126) may be provided in multiple numbers. Multiple permanent magnets (126) may be provided one per pole. In this embodiment, a configuration is shown in which a total of 6 permanent magnets (126) are provided. The 6 permanent magnets (126) can form 6 poles.

[0146] The arc portion (127) can be formed with a predetermined curvature. The arc portion (127) has a constant curvature along the circumferential direction. The arc portion (127) can be formed convexly toward the bearing hole (122).

[0147] The arc center (C) of the arc section (127) is located inside the rotor core (121). The arc center (C) of the arc section (127) may be located on an imaginary centerline passing radially through the center (O) of the rotor core (121).

[0148] Here, the arc center (C) means the center of the circle to which the arc of the arc part (127) belongs.

[0149] The arc center (C) of the arc section (127) may be positioned between the outer surface and the inner surface of the rotor core (121). The distance between the outer surface of the rotor core (121) and the arc center (C) of the arc section (127) is closer than the distance between the inner surface of the rotor core (121) and the arc center (C) of the arc section (127). The arc center (C) of the arc section (127) may be positioned adjacent to the outer surface of the rotor core (121).

[0150] The distance between the outer surface of the rotor core (121) and the arc center (C) of the arc portion (127) may be smaller than the thickness (1273) of the arc portion (127) to be described later.

[0151] The arc portion (127) may include an inner surface (1271), an outer surface (1272), and a thickness (1273).

[0152] The inner surface (1271) of the arc portion (127) may be positioned toward the outer surface of the rotor core (121). The inner surface (1271) of the arc portion (127) may be positioned spaced apart from the outer surface of the rotor core (121). The inner surface (1271) of the arc portion (127) may be a curved surface having a predetermined curvature. The inner surface (1271) of the arc portion (127) may form a part of a circle (hereinafter, inner circle (128)).

[0153] The outer surface (1272) of the arc portion (127) may be positioned toward the inner surface of the rotor core (121). The outer surface (1272) of the arc portion (127) may be positioned spaced apart from the inner surface of the rotor core (121). The outer surface (1272) of the arc portion (127) may be a curved surface having a predetermined curvature. The outer surface (1272) of the arc portion (127) may form a part of another circle (hereinafter, outer circle (129)).

[0154] The inner circle (128), to which the inner surface (1271) of the arc portion (127) belongs, may be positioned inside the outer circle (129), to which the outer surface (1272) of the arc portion (127) belongs. The center of the inner circle (128) may be positioned on the radial centerline together with the center of the outer circle (129).

[0155] The center of the inner circle (128) and the center of the outer circle (129) may be the same. The inner circle (128) and the outer circle (129) may form concentric circles. The diameter of the outer circle (129) is larger than the diameter of the inner circle (128).

[0156] The distance between the outer surface (1272) of the arc portion (127) and the inner surface of the rotor core (121) is closer than the distance between the inner surface (1271) of the arc portion (127) and the outer surface of the rotor core (121).

[0157] The thickness (1273) of the arc portion (127) may be formed between the inner surface (1271) of the arc portion (127) and the inner surface (1271) of the arc portion (127). The thickness (1273) of the arc portion (127) may be the difference between the radius of the inner circle (128) to which the inner surface (1271) of the arc portion (127) belongs and the radius of the outer circle (129) to which the outer surface (1272) of the arc portion (127) belongs.

[0158] The thickness (1273) of the arc portion (127) may be greater than the distance between the outer surface of the rotor core (121) and the arc center (C) of the arc portion (127). The thickness (1273) of the arc portion (127) may be smaller than the distance between the outer surface of the rotor core (121) and the inner surface (1271) of the arc portion (127).

[0159] The straight section (130) may extend radially from one end of the arc section (127). The straight section (130) may be formed in the shape of a cube.

[0160] The straight section (130) may be provided in multiple numbers. The multiple straight sections (130) may be configured to include a pair of first straight sections (130a) and second straight sections (130b). The first straight section (130a) may be provided at one end of the arc section (127), and the second straight section (130b) may be provided at the other end of the arc section (127).

[0161] The straight section (130) may be configured to include an inner surface (131), an outer surface (132), an end surface (133), and a thickness (134).

[0162] The inner surface (131) of the straight section (130) may be formed in a flat shape. The inner surface (131) of the straight section (130) may be connected to the inner surface (131) of the arc section (127). The inner surface (131) of the first straight section (130a) and the inner surface (131) of the second straight section (130b) may be arranged to face each other in the circumferential direction of the rotor core (121).

[0163] The outer surface (132) of the straight section (130) may be formed in a flat shape. The outer surface (132) of the straight section (130) may be connected to the outer surface (132) of the arc section (127). The length of the outer surface (132) of the straight section (130) may be extended longer than the length of the inner surface (131) of the straight section (130).

[0164] The outer surface (132) of the straight section (130) may be positioned facing in the opposite direction along the circumferential direction to the inner surface (131) of the straight section (130). The outer surface (132) of the first straight section (130a) and the outer surface (132) of the second straight section (130b) may be positioned away from the inner surface (131) of the first straight section (130a) and the inner surface (131) of the second straight section (130b), respectively, in the circumferential direction.

[0165] The inner surface (131) and the outer surface (132) of the straight section (130) may be spaced apart in the circumferential direction. The outer surfaces (132) of two straight sections (130) that are spaced adjacently in the circumferential direction may be positioned to face each other.

[0166] The first straight section (130a) of one of the two permanent magnets (126) adjacent in the circumferential direction and the second straight section (130b) of the other of the two permanent magnets (126) can be arranged adjacent to each other and parallel.

[0167] The end surface (133) of the straight section (130) may be formed in a flat shape. The end surface (133) of the straight section (130) may connect one end of each of the inner surface (131) and the outer surface (132) of the straight section (130). The end surface (133) of the straight section (130) may be extended parallel to the tangential direction of the rotor core (121).

[0168] One end of the inner surface (131) of the straight section (130) and one end of the end surface (133) can be connected by a first curved edge (1331). The first curved edge (1331) can be formed rounded in a curved shape. One end of the outer surface (132) of the straight section (130) and the other end of the end surface (133) can be connected by a second curved edge (1332). The second curved edge (1332) can be formed rounded in a curved shape.

[0169] The shortest distance between the outer surface of the rotor core (121) and the end surface (133) of the straight section (130) may be smaller than or equal to the shortest distance between the outer surface of the rotor core (121) and the center of the arc (C) of the arc section (127). In this embodiment, the distance between the outer surface of the rotor core (121) and the end surface (133) of the straight section (130) is shown to be smaller than the distance between the outer surface of the rotor core (121) and the center of the arc (C) of the arc section (127).

[0170] The thickness (134) of the straight section (130) can be formed between the inner surface (131) and the outer surface (132) of the straight section (130).

[0171] The angle (θ2) between the inner surfaces (131) of the first straight section (130a) and the second straight section (130b) and the angle (θ1) between the outer surfaces (132) of the first straight section (130a) and the second straight section (130b) may differ from each other. The angle (θ2) between the inner surfaces (131) of the first straight section (130a) and the second straight section (130b) may be greater than or equal to the angle (θ1) between the outer surfaces (132) of the first straight section (130a) and the second straight section (130b). In this embodiment, the angle (θ2) between the inner surfaces (131) of the first straight section (130a) and the second straight section (130b) is larger than the angle (θ1) between the outer surfaces (132) of the first straight section (130a) and the second straight section (130b).

[0172] The inner surface (131) of the straight section (130) may be formed to be inclined at a predetermined angle with respect to the outer surface (132) of the straight section (130). The thickness (134) of the straight section (130) may decrease as it moves radially outward from one end of the arc section (127).

[0173] Through this, torque ripple can be reduced.

[0174] The permanent magnet (126) can be formed symmetrically with respect to the radial centerline. Here, the radial centerline refers to an imaginary centerline passing radially through the center (O) of the rotor core (121) and the center of the arc length of the arc section (127). The center of the arc length of the arc section (127) refers to the center of the line extending along the circumference of the arc section (127).

[0175] A plurality of through holes (135a, 135b) may be provided in the rotor core (121). The through holes (135a, 135b) may be formed to penetrate in the axial direction of the rotor core (121). The plurality of through holes (135a, 135b) may be spaced apart in the circumferential direction. The plurality of through holes (135a, 135b) may include a first through hole (135a) and a second through hole (135b).

[0176] The first through hole (135a) may be positioned on the outer side of the arc portion (127). The first through hole (135a) may be positioned between the inner surface (131) of the arc portion (127) and the outer surface of the rotor core (121). One first through hole (135a) may be provided per pole. In this embodiment, six first through holes (135a) are shown formed. A plurality of first through holes (135a) may be positioned at 60-degree intervals.

[0177] The first through hole (135a) may be positioned on a radial centerline. The first through hole (135a) may be positioned in the center between the inner surface (131) of the arc portion (127) and the outer surface of the rotor core (121).

[0178] The second through hole (135b) may be positioned on the inner side of the arc portion (127). The second through hole (135b) may be positioned between the outer surface (1272) of the arc portion (127) and the inner circumferential surface of the rotor core (121). The second through hole (135b) may be positioned between the outer surfaces (1272) of two adjacent arc portions (127) in the circumferential direction. A plurality of second through holes (135b) may be positioned at 60-degree intervals.

[0179] The first through hole (135a) and the second through hole (135b) may be arranged radially opposite to each other.

[0180] Through this, the through hole can reduce the weight of the motor. The through hole can be used as a heat dissipation passage to release heat generated from the rotor (120). The through hole can improve the cooling performance of the motor.

[0181] The magnetization center (M) of the permanent magnet (126) can be formed on the outer side of the rotor core (121).

[0182] The magnetization center (M) refers to the central location within the motor where the electromagnetically generated magnetic flux is balanced. The magnetization center (M) can be set to minimize torque ripple as much as possible to minimize noise and vibration while satisfying the target torque.

[0183] The setting of the magnetization center (M) of the permanent magnet (126) will be described later.

[0184] Figure 7 is a conceptual diagram for explaining the comparison of magnet usage amounts according to the shape of the magnet.

[0185] Figure 8 is a graph for comparing (a) back electromotive force and (b) torque according to the shape of the magnet.

[0186] In this embodiment, the permanent magnet (126) is shown to be formed in a U-type shape. As described above, the U-type permanent magnet (126) may be configured to include an arc portion (127) and a plurality of straight portions (130).

[0187] Another type of permanent magnet (126) that can be compared to this is the C type.

[0188] Type C can only be formed in the shape of an arc. However, the arcs of Type U and Type C have different curvatures. For example, the curvature of a Type U arc can be greater than that of a Type C arc.

[0189] The U-type permanent magnet (126) has a larger area occupied by the permanent magnet (126) compared to the C-type permanent magnet (26). For example, the area of ​​the C-type permanent magnet (26) is 117.5 mm 2 It can be. The area of ​​the U-type permanent magnet (126) is 131.3 mm 2 It may be possible. In this case, the area occupied by the permanent magnet (126) of the U-type permanent magnet (126) is 11.8% larger than that of the C-type permanent magnet (26). The back electromotive force (BEMF) of the U-type permanent magnet (126) is about 8.1% higher than that of the C-type permanent magnet (26) (see FIG. 8 (a)). The torque of the U-type permanent magnet (126) is about 7.6% higher than that of the C-type permanent magnet (26) (see FIG. 8 (b)).

[0190] Through this, the U-type permanent magnet (126) has a high degree of shape freedom, allowing for an increased use of magnets compared to the C-type permanent magnet (26) in a limited space.

[0191] FIG. 9 is a conceptual diagram for explaining the angle (θ1, θ2) between the outer surface (132) and the inner surface (131) of the straight section (130) of the U-shaped magnet in FIG. 5, and the length (L) of the straight section (130) relative to the arc length (A) of the arc section (127).

[0192] FIG. 10 is a table showing the length ratio of the straight section (130) to the arc section (127), torque, and torque ripple according to the angle (θ2) between the inner surface (131) of the straight section (130) in FIG. 9.

[0193] FIG. 11 is a graph showing the change in (a) torque / torque ripple and (b) torque waveform according to the angle (θ2) between the inner surface (131) of the straight section (130) in FIG. 9.

[0194] When the above rotor is configured as a N pole, the angle between the outer surfaces (132) of the pair of straight sections (130a, 130b) may be (360 / N) ±10°. Here, N is a natural number greater than or equal to 2.

[0195] As described above in this embodiment, the angle (θ2) between the inner surfaces (131) of a pair of straight sections (130a, 130b) of the permanent magnet (126) is greater than the angle (θ1) between the outer surfaces (132) of a pair of straight sections (130a, 130b) of the permanent magnet (126).

[0196] Preferably, the angle (θ1) between the outer surface (132) of the straight portion (130) of the permanent magnet (126) may be 60 degrees based on the 6 poles. The angle (θ2) between the inner surface (131) of the straight portion (130) of the permanent magnet (126) may be within a range greater than 60 degrees and less than or equal to 80 degrees based on the 6 poles.

[0197] According to the present embodiment, in order to solve the noise and vibration problems that occur as the motor becomes smaller and faster, efforts are required to minimize torque ripple.

[0198] The torque required for the international standard Ashrae test conditions for refrigerators may be 0.164 N·m. Under the above Ashrae conditions, the torque ripple may be 30%. In this embodiment, the goal was to achieve a torque ripple of 12% or less, which is 40% of the existing torque ripple. To reduce the torque ripple, the angle (θ2) between the inner surface (131) of the straight section (130) of the permanent magnet (126) is made larger than the angle (θ1) between the outer surface (132) of the straight section (130) of the permanent magnet (126).

[0199] As a result of the analysis, when the angle (θ2) between the inner surface (131) of the straight section (130) of the permanent magnet (126) is in the range of 60 to 80 degrees, the torque is slightly reduced and the torque ripple is greatly improved. For example, when the angle (θ2) between the inner surface (131) of the straight section (130) of the permanent magnet (126) increases from 60 degrees to 70 degrees, the torque decreases slightly from 0.165 (N·m) to 0.164 (N·m), but the torque ripple decreases significantly from 14.4% to 9.8%. When the angle (θ2) between the inner surface (131) of the straight section (130) of the permanent magnet (126) is 80 degrees or more, the torque ripple is no longer improved and the torque performance deteriorates.

[0200] Depending on the angle of the straight section (130) of the permanent magnet (126), the ratio of the straight section (130) length (L) to the arc length (A) can also be determined. Referring to the table in FIG. 10, when the angle of the straight section (130) of the permanent magnet (126) is 80 degrees, the ratio of the straight section (130) length (L) to the arc length (A) can be 36%.

[0201] The ratio of the length (L1) of the straight section (130) of the permanent magnet (126) to the arc length (A1) may be within 36%.

[0202] Here, the angle of the straight section (130) of the permanent magnet (126) can be defined as the angle (θ2) between the inner surface (131) of the straight section (130) of the permanent magnet (126). The length (L) of the straight section (130) can be defined as the radial length (Lo) extending along the center of the straight section (130). The length (L) of the straight section (130) can be defined as the length (L1) of the inner surface (131) of the straight section (130). The length (L) of the straight section (130) can be defined as the length (L2) of the outer surface (132) of the straight section (130).

[0203] The arc length (A) of the arc portion (127) can be defined as the circumferential length (Ao) extending along the center of the arc portion (127). The arc length (A) of the arc portion (127) can be defined as the arc length (A1) of the inner surface (1271) of the arc portion (127). The arc length (A) of the arc portion (127) can be defined as the arc length (A2) of the outer surface (1272) of the arc portion (127).

[0204] The length (L2) of the outer surface (132) of the straight section (130) may be greater than the length (L1) of the inner surface (131) of the straight section (130). The arc length (A2) of the outer surface (1272) of the arc section (127) may be greater than the arc length (A1) of the inner surface (1271) of the arc section (127).

[0205] By doing so, torque ripple can be significantly reduced when the angle (θ2) between the inner surface (131) of the straight portion (130) of the permanent magnet (126) is limited to within the range of 60 to 80 degrees.

[0206] FIG. 12 is a conceptual diagram for explaining the comparison of the distance between the rotor center (O) and the magnetization center (M) of the permanent magnet (126) in FIG. 2, the distance between the rotor center (O) and the arc center (C), and the distance between the rotor center (O) and the intersection point between the pole shoe (114) and the teeth (113) of the stator (100).

[0207] FIG. 13 is a table showing the change in torque and torque ripple according to the distance between the rotor center (O) and the magnetization center (M) of the permanent magnet (126) in FIG. 12.

[0208] FIG. 14 is a graph showing (a) torque / torque ripple and (b) torque waveform according to the distance between the rotor center (O) and the magnetization center (M) of the permanent magnet (126) in FIG. 12.

[0209] To minimize torque ripple, the center of magnetization (M) can be set.

[0210] In this embodiment, as described above, the magnetization center (M) can be set to be located on the outer side of the rotor (120). The distance from the center (O) of the rotor core (121) to the magnetization center (M) of the permanent magnet (126) can be set to be greater than the radius (R) of the rotor (120). The distance from the center (O) of the rotor core (121) to the magnetization center (M) of the permanent magnet (126) can be 1.05 times or less the distance from the center (O) of the rotor core (121) to the intersection point of the pole shoe (114) and the tooth (113) of the stator (100).

[0211] R <M≤1.05ⅩD

[0212] M (Magnetization Center): Distance from the center (O) of the rotor core (121) to the magnetization center (M) of the permanent magnet (126), R: Radius of the rotor (120), D: Distance from the center (O) of the rotor core (121) to the intersection point of the pole shoe (114) and the tooth (113) of the stator (100).

[0213] When the distance from the center (O) of the rotor core (121) to the magnetization center (M) of the permanent magnet (126) increases from 25 mm (0.9D, 1R) to 29 mm (1.05D, 1.16R), the torque decreases slightly, but the torque ripple decreases significantly.

[0214] When the distance from the center (O) of the rotor core (121) to the magnetization center (M) of the permanent magnet (126) is 29 mm (1.05 D, 1.16 R) or more, the torque ripple is no longer improved and the torque performance deteriorates.

Claims

1. Multiple permanent magnets; and It includes a rotor core having a plurality of magnet receiving portions for accommodating the plurality of permanent magnets, and Each of the above plurality of permanent magnets, based on the magnetic pole surface acting on the rotor core, Support Department; and It includes a pair of straight sections extending radially from each end of the above-mentioned arc section, and Each of the above plurality of permanent magnets is formed as a single unit, Rotor.

2. In Paragraph 1, The above pair of straight sections is, Each is formed in the shape of a cuboid, and A pair of inner surfaces arranged to face each other in the circumferential direction of the rotor core; and It includes a pair of outer surfaces arranged to be spaced apart in the circumferential direction from the pair of inner surfaces mentioned above, and The angle between the pair of inner surfaces is formed to be larger than the angle between the pair of outer surfaces. Rotor.

3. In Paragraph 2, The above plurality of permanent magnets are provided as one per pole, and When the above rotor is configured as a N pole, The angle between the outer surfaces of the above pair of straight sections is (360 / N) ±10°, and The angle between the inner surfaces of the above pair of straight sections is greater than the angle between the outer surfaces, Rotor.

4. In Paragraph 3, The angle between the outer surfaces of the above pair of straight sections is (360 / N)°, Rotor.

5. In Paragraph 3, The plurality of permanent magnets are spaced apart in the circumferential direction of the rotor core, and A straight section of one of the two permanent magnets adjacent in the circumferential direction and a straight section of the other of the two permanent magnets are arranged adjacent to and parallel to each other. Rotor.

6. In Paragraph 1, The inner surface of one of the pair of straight sections is formed to be inclined with respect to the outer surface of the one straight section. Rotor.

7. In Paragraph 1, The above pair of straight sections is, Each is formed in the shape of a cuboid, A pair of inner surfaces arranged to face each other in the circumferential direction of the rotor core; and It includes a pair of outer surfaces arranged to be spaced apart in the circumferential direction from the pair of inner surfaces mentioned above, and The thickness of the straight section is formed between the inner and outer surfaces of the pair of straight sections, and the thickness of the straight section decreases as it moves outward in the radial direction from the arc section. Rotor.

8. In Paragraph 7, The radial length of the outer surface is formed to be longer than the radial length of the inner surface. Rotor.

9. In Paragraph 1, The above arc section is, An inner surface positioned toward the outer surface of the rotor core and formed in an arc shape; and It includes an outer surface that is positioned toward the center of the above-mentioned rotor core and is formed in an arc shape, and The arc centers of the inner and outer surfaces of the above-mentioned arc portion are the same, and the outer surface of the above-mentioned arc portion faces the center of the rotor core. Rotor.

10. In Paragraph 9, The thickness of the arc portion is formed between the outer surface and the inner surface of the arc portion, and the thickness of the arc portion is constant along the circumferential direction. Rotor.

11. In Paragraph 1, The above permanent magnet is symmetrical with respect to a virtual centerline passing through the center of the rotor core and the center of the arc of the arc portion. Rotor.

12. In Paragraph 2, The angle between the inner surfaces of the above pair of straight sections is greater than 100% and less than or equal to 133.3% compared to the angle between the outer surfaces of the above pair of straight sections. Rotor.

13. In Paragraph 1, The radial length extending along the center of one of the pair of straight sections is smaller than the arc length extending along the center of the arc section. Rotor.

14. In Paragraph 1, The length of the straight section is within 36% of the arc length of the arc section, Rotor.

15. In Paragraph 1, The magnetization center of each of the plurality of permanent magnets is located on the outer side of the rotor core. Rotor.

16. In Paragraph 15, The distance from the center of the rotor core to the magnetization center of the permanent magnet is greater than the distance from the center of the rotor core to the center of the arc of the arc portion, Rotor.

17. In Paragraph 1, The shortest separation distance between the outer surface of the rotor core and the center of the arc of the arc portion is greater than or equal to the shortest separation distance between the outer surface of the rotor core and the outer end of the straight portion. Rotor.

18. In Paragraph 1, The above arc section is, An inner surface positioned toward the outer surface of the rotor core and formed in an arc shape; and It includes an outer surface that is positioned toward the center of the above-mentioned rotor core and is formed in an arc shape, and The arc centers of the inner and outer surfaces mentioned above are the same, The thickness of the arc portion is formed between the outer surface and the inner surface of the arc portion, and On an imaginary centerline passing through the center of the rotor core and the arc center of the arc portion, the thickness of the arc portion is greater than or equal to the distance between the inner surface of the rotor core and the outer surface of the arc portion, and less than or equal to the distance between the outer surface of the rotor core and the inner surface of the arc portion. Rotor.

19. Housing; A stator coupled to the inner side of the above housing; and It includes a rotor spaced apart with an air gap inside the stator and rotating about a rotation axis with respect to the stator. The above rotor is, Multiple permanent magnets; and It includes a rotor core having a plurality of magnet receiving portions for accommodating the plurality of permanent magnets, and Each of the above plurality of permanent magnets is, Support Department; and It includes a pair of straight sections extending radially from each end of the above-mentioned arc section, and A motor in which each of the above plurality of permanent magnets is formed as a single unit.

20. In Paragraph 19, Each of the above plurality of permanent magnets has a magnetization center located on the outer side of the rotor core, motor.

21. In Paragraph 20, The above stator is, A stator core having a plurality of teeth and slots alternately arranged along the circumferential direction; and It includes a stator coil wound on the stator core through the slot above, and A pole shoe is formed to protrude in the circumferential direction from the radially inner end of the above tooth, and The distance from the center of the rotor core to the magnetization center of the permanent magnet is greater than the radius of the rotor core and smaller than 1.05 times the distance from the center of the rotor core to the intersection point of the teeth and the pole shoe, motor.

22. In Paragraph 19, The above pair of straight sections is, Each is formed in the shape of a cuboid, A pair of inner surfaces arranged to face each other in the circumferential direction of the rotor core; and It includes a pair of outer surfaces arranged to be spaced apart in the circumferential direction from the pair of inner surfaces mentioned above, and A motor in which the angle between the pair of inner surfaces is formed to be larger than the angle between the pair of outer surfaces.

23. In Paragraph 22, The above plurality of permanent magnets are provided as one per pole, and When the above rotor is configured as a N pole, The angle between the outer surfaces of the above pair of straight sections is (360 / N) ±10°, and The angle between the inner surfaces of the above pair of straight sections is greater than the angle between the outer surfaces of the above pair of straight sections. motor.

24. In Paragraph 23, A rotor in which the angle between the outer surfaces of the above pair of straight sections is (360 / N)°.

25. In Paragraph 23, The plurality of permanent magnets are spaced apart in the circumferential direction of the rotor core, and A straight section of one of the two permanent magnets adjacent in the circumferential direction and a straight section of the other of the two permanent magnets are arranged adjacent to and parallel to each other. Rotor.

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